#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	double i,n;
	double sum = 0;
	n = -1;
	for (i = 1; i <= 100; i++) {
		n = n * (-1);
		sum =sum+n / i;
		
	}
	printf("%.2lf", sum);
	return 0;
}